Various telecommunication systems require communication cables comprising an odd number of conductor pairs. A commonly used cable for such purposes is the twenty-five pair, category five cable. This cable, like other cables, must comply with associated TIA/EIA requirements. Various cable construction techniques have been tried by cable manufacturers in an attempt to pass the power sum near-end crosstalk (NEXT) specification for TIA/EIA twenty-five pair category five cables.
For a plenum product, the use of a filler having a star configuration would not allow the product to pass the UL 910 burn test. This is so because the star filler greatly increases the percentage of combustible plastics when compared to a copper heat sink based upon presently known state of the art materials.
The layout of the pairs of conductors comprising a cable is critical in the cable passing the TIA/EIA power sum NEXT electrical specification. One of the more successful attempts utilized a cable construction having the twenty-fifth pair jacketed and used as a center filler with six quads using two or more different pair lay schemes and one or more different quad lay lengths (L) surrounding the filler. However, the location of the twenty-fifth pair inside the filler causes increased installation times and potential for damage. For example, in cables utilizing such a cable layout, the twenty-fifth pair is prone to damage when stripping off the end of the rather thick filler jacket during installation.
Several different cable constructions have been attempted in the past, including having the twenty-fifth pair pulled straight in between two of the quads, having the twenty-fifth pair placed by the center along with the tube filler, and laying the twenty-fifth pair on the outside of the cable core. However, the cables fail to meet the TIA/EIA power sum NEXT requirements for the twenty-fifth pair. In addition, the cables also failed signal reflection loss (SRL), impedance, and attenuation requirements due to instability in the twenty-fifth pair.
It was also found that the twenty-fifth pair interfered with the pairs in the quads closest to it. The damage to the insulation of the twenty-fifth pair was caused by the twenty-fifth pair being pinched between quads, or being pinched between the quads and the filler, or being pinched between the core and the jacket.
A cable construction involving jacketing twelve and thirteen pairs of conductors together to yield a twenty-five pair cable has also been attempted with limited success. For example, the resulting shape of the cable is not round, thus making it harder to install, specifically with regard to conduit fill.